Friday, September 03, 2010

Interference on 30m

I was in the shack making a few adjustments to the Echolink software configuration. The K3 was on 30m APRS with the speaker volume turned down to almost inaudible. Suddenly, at about 1410 UTC, I heard a buzzing type of interference. I looked at the TrueTTY waterfall and saw there were interference bars every 50Hz right across the screen, strong enough to prevent anything from being decoded.

50Hz is the mains frequency here in the UK. With a sinking feeling my immediate thought was that one of the neighbours had discovered a new way to make the HF bands unusable. Then I remembered that Lynn, KJ4ERJ had posted a screenshot of similar interference only the day before in an APRS forum. I checked back, and sure enough the interference Lynn had seen in Florida was exactly the same.

I don't know what it is, but I don't think even my neighbours are capable of generating interference that could be heard across the Atlantic. It's still going strong 30 minutes later. I haven't seen an HF band wiped out like this since the Woodpecker fell silent back in the '80s. Well, at least I've got Echolink!

4 comments:

Paul - PAØPSY said...

Hello Julian, I do have the same QRM on 30 meter at say time and sometimes on 20 meter as well. They told me it has to with flat screen televisions. But I don't know if that's true. In the evening this qrm is gone on 30 meter. 73 Paul

GW0KIG said...

Julian,

I have this too from time to time. only on 30 metres. sometimes it lasts for a few hours. I haven't been able to pinpoint it though.

73 Kevin

Lynn (D) said...

The general consensus on 9/1 was an Over-The-Horizon radar on Cyprus compliments of the RAF - so in effect, it was your neighbors! Here's a link to the APRS Messenger waterfall I was seeing.

http://tinyurl.com/Interfere-30m

Today's interference was also observed in Sydney by VK2IO, but I didn't get a chance to check my waterfall until it was over.

Some interesting links that came out of the today's discussion:

http://en.wikipedia.org/wiki/RAF_Akrotiri

And the woodpecker antenna:

http://www.artificialowl.net/2008/12/abandoned-giant-duga-3-system-antenna.html

I want one of those antennas!

Lynn (D) - KJ4ERJ - Author of APRSISCE for Windows Mobile and Win32

PE4BAS, Bas said...

Yes, defenitely OTH from Cyprus. Heard many times on 30m here. Nothing you can do about it, only change bands. 73, Bas